In a case of a motor including a rotor in which arc-shaped permanent magnets are arranged in a rotor core so that convex portion sides thereof face a center side of the rotor, with the formation of the permanent magnets into the arc shape, the surface areas thereof can be increased to increase an amount of a magnetic flux generated in each of the permanent magnets of the rotor. On the other hand, the above-mentioned motor has the following problems. A core corresponding to a magnetic-pole surface portion of the permanent magnet is large, and hence it is difficult to control a magnetic flux density on the magnetic-pole surface portion. Vibration and noise are large due to a harmonic component of a magnetic flux density distribution. A leakage magnetic flux is easily caused between the adjacent magnets. The vicinities of end portions of the magnet are easily partially demagnetized.
As the motor in which the permanent magnets are arranged as described above, the motor disclosed in Patent Literature 1 is given. In Patent Literature 1, there is disclosed a permanent magnet motor including a rotator in which a plurality of permanent magnets for magnetic poles, which have an arc shape in cross-section, are arranged in a rotator core so that each of convex portion sides thereof faces a center side of the rotator core. In the configuration, the rotator is rotatably arranged in a stator core having an approximately cylindrical shape. Further, in the above-mentioned permanent magnet motor, the size of an air gap between an outer peripheral surface of the rotator core and an inner peripheral surface of the stator core is varied in a circumferential direction. Specifically, in each of the magnetic poles, the gap is increased as approaching from a region corresponding to a center portion of the magnetic pole in the circumferential direction to a region corresponding to a portion between the magnetic poles.
Further, in Patent Literature 2, there is disclosed a motor including a stator having a plurality of slots, and a rotator being arranged so as to be opposed to the stator with an interval and having magnet receiving holes for inserting permanent magnets. Further, in the motor, an outer peripheral portion of the rotator includes first curved parts each intersecting with a d-axis of a main magnetic pole portion so that a convex portion side thereof faces an outer peripheral side, and second curved parts each intersecting with a q-axis of an auxiliary magnetic pole portion so that a convex portion side thereof faces the outer peripheral side. The first curved parts and the second curved parts are alternately connected to each other. A center of a radius of the first curved part of the main magnetic pole portion coincides with a center of a shaft hole of the rotator. A radius of the second curved part of the auxiliary magnetic pole portion is larger than the radius of the first curved part of the main magnetic pole portion. Further, assuming that, regarding the shaft hole of the rotator as a center, an opening angle of the first curved part is defined as θ1, an opening angle of the second curved part is defined as θ2, and an opening angle of a tooth end portion between the slots of the stator is defined as θ3, θ1≦θ2 and θ1≦θ3 are satisfied.